function [Az_R] = EffSSN(Az)
%
% Effective Sun Spots Number (Az_R)
%
%DESCRIPTION:
%This function computes the Effective Sun Spots Number as function of the
%Effective Ionisation Level (Az).
%
%PROTOTYPE:
% [Az_R] = EffSSN(Az)
%
%--------------------------------------------------------------------------
% INPUTS:
%   Az         [1x1]       Effective Ion. Level      [-]
%--------------------------------------------------------------------------
% OUTPUTS:
%   Az_R       [1x1]       Effective Sun Spots Nr.   [-]
%--------------------------------------------------------------------------
%
%NOTES:
% - The Az_R is like R_12.
%
%CALLED FUNCTIONS:
% (none)
%
%UPDATES:
% (none)
%
%REFERENCES:
% [1] "Ionospheric Correction Algorithm for Galileo Single-Frequency Users"
%      - European GNSS (Galileo) Open Service
% [2] "Electron Density Models and Data for Transionospheric Radio
%      Propagation" - Report ITU-R P.2297-1 (05/2019)
%
%AUTHOR(s):
%Luigi De Maria, Matteo D'Addazio, 2022
%

%% Main Code

%Effective Sun Spots Number

Az_R = sqrt(167273 + (Az - 63.7)*1123.6) - 408.99;

end